短时气温冻融周期内土坡浅层的水热状况分析

为揭示短时冻融周期内土坡浅层的水热状况特征,选取典型短时冻土区域,采用现场气象监测与数值模拟相结合的技术手段对短时气温冻融周期内土坡浅层水热状况进行分析。结果表明:在3个月冻期总持续时间内,共有18次气温冻融周期,其中16次为1 d气温冻融周期,1次为2 d气温冻融周期,1次为6 d气温冻融周期。气温冻融周期内最低气温为-4.4℃,最高气温为10.8℃;日辐射峰值范围为41~827 W/m~2;平均风速为3.5~3.7 m/s;大气中水汽接近饱和状态。6 d与1 d气温冻融周期内土壤最大冻结时间分别为32 h与5 h,最大冻深分别为10 cm与5 cm,土壤含冰率分别为0.16与0.14,短时冻区应重点关注边坡浅层10 cm以内土壤强度的冻融损伤。1 d气温冻融周期内,土壤冻结时段一般为3∶00—8∶00之间。土壤冻结的开始时刻取决于最低气温,而土壤冻结持续时间取决于太阳辐射高低,若土壤冻结时间与太阳辐射时间相重叠或者气温处于土壤冻结温度以下的持续时间小于1.5 h,边坡土壤不易冻结。因此,同一边坡的阳面与阴面在土壤冻结开始时刻与冻结持续时间存在较大差异。

Hydrothermal Regime Analysis on Shallow Layer of Soil Slope under Short-term Freeze-thaw Cycles

Taking typical short-term frozen zone in Fujian province of China as an example,hydrothermal regime on shallow layer of soil slope in short-term freeze-thaw cycles were analyzed based on the combination of meteorological monitoring method and numerical simulation.The results show that there are 18 times of freeze-thaw cycles of air temperature from Dec.2013 to Feb.2014 which include 16 times of one day freeze-thaw cycle of air temperature,1 time of two days freeze-thaw cycle of air temperature and 1 time of six days freeze-thaw cycle of air temperature.During the short-term freeze-thaw cycles of air temperature,the minimum and maximum of air temperature can reach-4.4 Cand 10.8 C,respectively.Peak of daily radiation ranges from 41 to 827 W/m2,and average wind speed is between 3.5 and 3.7 m/s.Atmospheric humidity is close to saturation.During six days or one day of freeze-thaw cycle of air temperature,maximum duration of the soil freezing is between 32 h and 5 h,maximum frozen depth amount to respectively 10cm with 5cm,ice content of frozen soil is 0.16 and 0.14,respectively.In view of freezing-thawing damage in short-term frozen area,strength degradation of soil slope at the depth range of 0～ 10 cm should be focused on.During one day of freeze-thaw cycle of air temperature,soil freezing time is between 3a.m and 8a.m.The initial freezing time of soil depends on minimum air temperatures and freezing time of soil depends on intensity of daily radiation.Shallow layer of soil slope is not easy to be frozen when air temperature below soil freezing temperature and solar radiation is in coexistence or when the duration of air temperature below soil freezing temperature is less than 1.5 h.So,initial freezing time and duration of the freezing between the sunny slope and the shady slope at the same short-term frozen zone are big divergence.